Method and apparatus for assisting percutaneous computed tomography-guided surgical activity

ABSTRACT

A method and an apparatus for assisting percutaneous computed tomography-guided surgical activity inside a human or animal body, such as withdrawal of body tissue or body liquid sample, withdrawal of excess body liquid, insertion or injection, said method for determining insertion depth, transversal insertion angle and craniocaudal insertion angle for a needle-type surgical instrument to be inserted into the human or animal body from an insertion entry point on a skin surface of said body to a target inside said body. From a first tomography image coordinate values of said entry point are determined, and from said first or a second tomography image coordinate values of said target point are determined. Based on said coordinate values values of said insertion depth, transversal insertion angle and craniocaudal insertion angle are calculated. Said calculated values are applied to an instrument insertion guiding apparatus positioned adjacent said body in no physical contact therewith, said apparatus having a laser which provides a laser beam, manipulating adjustment means on said apparatus to let the laser beam assume the values of transversal insertion angle and craniocaudal insertion angle and to let the laser beam point at the entry point. The instrument with a needle pointed end thereof is located at said entry point and a longitudinal axis of the instrument is aligned with said laser beam, the aligning being made by letting a distal end face of said instrument be pointed at by said laser beam.

This application is a divisional of U.S. patent application Ser. No.08/885,077 filed Jun. 30, 1997 now U.S. Pat. No. 6,021,342.

The present invention relates to a method and an apparatus for assistingpercutaneous computed tomography-guided surgical activity inside a humanor animal body, such as withdrawal of body tissue or body liquid sample,withdrawal of excess body liquid, insertion or injection. The method isintended for determining insertion depth, transversal insertion angleand craniocaudal insertion angle for a needle-type surgical instrumentto be inserted into the human or animal body from an insertion entrypoint on a skin surface of said body to a target inside said body. Saidapparatus is related to said surgical activity when there is used aneedle-type surgical instrument to be inserted into the human or animalbody from an insertion entry point on a skin surface of said body to atarget inside said body.

BACKGROUND OF THE INVENTION

Computed tomography (CT) is an X-ray examination method wherebysectional images, so-called slices, are taken of the body of a patientby letting an X-ray tube device rotate 360 degrees about the patient.The patient is located on a moveable table which moves in incrementalsteps slowly through an opening or tunnel where the X-ray tube devicerotates about the tunnel. The body of the patient is thereby sectionedby a CT computer approximately like cutting a bread in slices. Each ofthese slices are then viewed by an operator on a display. The sliceimages are taken at right angles to the longitudinal axis of the patientbody, and each image has a number corresponding to an address along thelongitudinal axis (z-axis). It is possible to select both the thicknessof the slices and the interdistance between the slices. The normal slicethickness is 7 or 10 millimetres thickness edge-to-edge.

It is sometimes necessary to introduce a thin instrument needle into apatient and towards a region to be investigated, and e.g. remove sometissue cells in order to establish whether e.g. a malignant tumour ispresent. If such tumour is large and close to the skin surface, suchbiopsy procedure is normally not complicated. However, if the tumour issmall and/or lies deeply inside the body, it will be appreciated that itcan be very difficult to hit the target tumour exactly with the needle.

Present day practice is that first, a series of computed tomographyslice images are made of the patient. Thereafter, the various images tobe shown on the display are searched until an image is found where thetumour is clearly shown.

Thereafter, an electronic marking is made on the display correspondingto the spot on the skin where it is desired to have the point ofinsertion, e.g. 5 centimetres to the right of a centreline. Thereafter,the patient table is moved to the address or table position on the imagein question, and by means of a guide light, a line is drawn transverselyof the body of the patient, corresponding to the longitudinal axisaddress of the image in question. It is then measured by means of aruler 5 centimetres to right from the centreline, and a marking is madethereat on the body. At that marking there is placed a small metalindicator, e.g. the point of a syringe which is attached to the skin bymeans of adhesive tape and parallel to the longitudinal axis of thepatient body. Again, the image in question is taken, and at thisoccasion the metal indicator will appear on the image at the intendedpoint of insertion, and it is thereby possible to check that the pointof insertion corresponds to that which was intended.

The next step is to place two electronic crosses on the display, one atthe point of insertion and one at the tumour. The CT computer will thencalculate the distance between the two points and the angletherebetween. The distance may e.g. be 7.5 cm, and the angle e.g. 21.5degrees to the right relative to the vertical. Local anaesthetics isapplied to the region of the point of insertion, and an instrumentneedle is thereafter moved 7.5 cm into the patient body.

One substantial drawback of such procedure is that the proper angle wheninserting the needle has to be determined by the radiologist more orless by eye measure. Using devices which can be placed on the human bodyand in physical contact with the instrument and its needle arecumbersome in use, inaccurate and must be thoroughly desinfected afterused or be of a single use type. Such devices are therefore expensive inuse, and the risk of infection is present, unless absolute sterileconditions are present during the repeated attempts to hit the target,e.g. a tumour.

Therefore, in practice, the radiologist more than often simplydetermines the angle of the insertion of the needle based on eye measurejudgement only. As will be appreciated, it is not at all easy tointroduce a needle at an exact angle of 21.5 degrees based on eyemeasure only. In addition, the insertion is to be made in a planeexactly 90 degrees to the longitudinal axis of the patient body. Thus,using the present day method of so-called free-hand puncture it isfrequently required to make several puncture attempts before the targetis hit. After each puncture attempt, new slice images must be taken tocheck whether the needle point of the instrument has hit the target ornot. Sometimes, it is experienced that the instrument needle has notbeen introduced into the body in plane 90 degrees to the longitudinalaxis of the patient body, and the needle can thereby have moved out ofthe slice plane. It will be recognised by any surgeon that difficultpuncture operations are extremely time-consuming, and in the worst casemay take more than an hour. This yields an increased risk ofcomplications, such as internal bleedings, in addition to the obviousdiscomfort of the patient. Further, a computed tomography machine is avery expensive device which costs approximately one million US dollarsor more. Thus, the cost of using a machine per time unit is important.Therefore, this is more than often a problem in the medical examinationprocess within a hospital, and time consuming attempts to hit the targetwithin the patient body may occupy the CT-machine for an unacceptablelong period of time.

In order to solve the problem of introducing the instrument needle intothe patient body at a correct angle, some hospitals use different typesof puncture accessories, both mechanical and optical. In practice, theyare not widely used, simply because their operation is somewhatcumbersome.

From the prior art there are known many methods and apparatus forassisting percutaneous computed tomography-guided surgical activityinside a human or animal body. Many apparatus and methods, however,strongly rely on the apparatus being clamped onto the human body, e.g.the head of a human, such as described e.g. in U.S. Pat. No. 5,116,344.Other devices such as that described in Austrian patent 387903 rely onthe apparatus being attached to the human body at the insertion pointand with the needle type surgical instrument extending through a guidetube of the apparatus. Such an apparatus requires either thoroughcleaning after use or that the apparatus is simply a single-useapparatus, which makes it rather expensive.

U.S. Pat. No. 4,733,661 relates to a hand-held apparatus for insertionof the surgical instrument, but is difficult to use, because the surgeonmust use one hand on the apparatus and one hand on the surgicalinstrument to be inserted, which may prove difficult in practice.

Also, the surgical instrument is in contact with the device and thoroughcleaning of the device after use is absolutely required.

U.S. Pat. No. 5,308,352 relates to a stereotactic device supported by aframe structure over the platform on which the human or animal body isplaced. The device is put into a physical contact with the body and inthat position clamped to the supporting frame. Thereafter, the surgicalinstrument is inserted into the body through a pair of guide holes.Thus, the stereotactic device according to U.S. Pat. No. 5,308,352 alsorequires thorough cleaning after use, which makes it complicated andexpensive for practical purposes.

A stereotactic instrument similar to that of U.S. Pat. No. 4,733,661 isalso known from European patent publication 0414130. However, the samedeficiencies as with other prior art devices of the same type also applyto that of European patent application 041430.

The present invention, however, is intended to provide a method and anapparatus in which the assistance in the surgical activity is based on anon-physical contact between the apparatus and the human or animal bodyor between the apparatus and the needle-type surgical instrument to beinserted into said body.

SUMMARY OF THE INVENTION

According to the present invention, the method comprises

determining from a first tomography image co-ordinate values of saidentry points related to a first tomography slice position alongcraniocaudal direction, and horizontal and vertical directionstransversely of said craniocaudal direction at said first position,

determining from said first or a second tomography image co-ordinatevalues of said target point related to said first or a second tomographyslice position along craniocaudal direction, and horizontal and verticaldirections transversely of said craniocaudal direction at said first orsecond position, and

calculating from said first and second co-ordinate values throughprinciple of trigonometry values of said insertion depth, transversalinsertion angle and craniocaudal insertion angle.

Further, the method according to the invention comprises applying saidvalues of said transversal insertion angle and craniocaudal insertionangle to an instrument insertion guiding apparatus positioned adjacentto said body in no physical contact therewith, said apparatus having alaser which provides a laser beam and manipulating adjustment means onsaid apparatus to let said laser beam assume said values of transversalinsertion angle and craniocaudal insertion angle and to let said laserbeam point at said entry point.

Further, the method comprises locating said instrument with a needlepointed end thereof at said entry point and aligning a longitudinal axisof said instrument with said laser beam. Said instrument will be in nophysical contact with said apparatus. In order to carry out saidaligning, a distal end face of the instrument is pointed at by saidlaser beam.

A laser carrying arm or transverse member of said apparatus is locatedto lie horizontally above the body at right angles to the craniocaudaldirection. The laser beam can provide a spot or cross-hair like image onsaid distal end face.

Thus, the present method provides a non-physical contact with the humanor animal body in the process of assisting percutaneous computedtomography-guided surgical activity.

The apparatus, according to the invention comprises a laser beamgenerator device, adjustment means physically linked with said device,said adjustment means for adjusting direction of said beam based oncomputed transversal insertion angle data and craniocaudal insertionangle data obtained from computed tomography slice data, said beamdirection being adjustable to be coaxial with insertion direction of aneedle-type surgical instrument to be inserted into the human or animalbody from the insertion entry point on the skin surface of said body tothe target inside said body, angle indicator means associated with saidadjustment means for indication of said insertion angles, power supplymeans and means supporting the apparatus so as to be in no physicalcontact with said body.

According to a further embodiment of the apparatus, there is providedinsertion angle calculating means for calculating a transversalinsertion angle and craniocaudal insertion angle values based on firsttomography image co-ordinate values of said entry point related to afirst tomography slice position along a craniocaudal direction, andhorizontal and vertical directions transversely of said craniocaudaldirection at said first position, and second tomography imageco-ordinate values of said target point related to said first or asecond tomography slice position along craniocaudal direction, andhorizontal and vertical directions transversely of said craniocaudaldirection at said first or second position.

Further, the apparatus provides insertion depth calculating means forcalculating insertion depth into said body of said surgical instrumentfrom said first and second co-ordinate values through principles oftrigonometry.

The apparatus may comprise an arm carrying said laser beam generatordevice, said arm being located horizontally and at right angles to thecraniocaudal direction. In addition, the apparatus can be provided withan auxiliary laser beam generator device providing a vertical lightplane parallel to the cranocaudal direction.

According to even a further embodiment of the apparatus, said supportingmeans has a base member, an upright member extending from said basemember, and a transverse member or arm extending from a top region ofthe upright member. Further, said base member suitably rests on a floor.

As an alternative, said supporting means is attached to a bed basemember forming a support for a computed tomography machine bed movabletherealong and supporting said human or animal body, said supportingmeans having an upright member and a transverse member or arm extendingfrom a top region of the upright member. Suitably the supporting meansis slidably attached to said gantry means to be slidable in acraniocaudal direction.

According to a further alternative, said supporting means is suspendedfrom a ceiling or from a top part of the CT apparatus above a movablecomputed tomography machine bed which supports said human or animalbody, and said supporting means has a horizontally located transversemember or arm.

Said laser beam generator device is movable along said transverse memberand selectively is fixable at arbitrary locations therealong.

Said device is movable along said transverse member or arm and isselectively fixable at arbitrary locations therealong.

Further, said upright member is suitably a height adjustable telescopicdevice.

In the said further alternative said supporting means has means foradjusting a vertical level of said transverse member or arm.

Thus, above the CT-movable table the laser beam generator device ismovable along the transverse member or arm being a rail means. The lasercan be angled generally in two directions, both transversely of thelongitudinal axis of the patient body and in the craniocaudal direction.The rail can be installed horizontally, e.g. 1 meter above the patientand is located 90 degrees relative to the CT table longitudinaldirection. The laser is movable to the left or the right of thelongitudinal axis of the patient body along said rail. The rail issupported by the upright member or is suspended from a ceiling. Thepoint of insertion on the skin is marked by use of suitable ink. Thelaser is set to the correct angle, i.e. the angle which has been read onthe display, and is moved either to the right or the left relative tothe longitudinal axis of the patient body, such that the laser lightbeam illuminates exactly the marked point of insertion. Adjustment alongthe longitudinal axis of the patient body in order to have the laserlight beam hitting the point of insertion is made by driving theCT-table towards the head and/or the foot end, which operation can bemade to the accuracy of millimetres.

With the present invention the skin at the point of insertion of theinstrument needle is properly cleaned and the puncturing needle end isplaced on the skin at the point of insertion, i.e. where the laser beamspot or cross-hair image is seen. The instrument needle is kept in suchposition that the laser light beam hits the rear centre face of theinstrument. Thereafter, the needle is moved into the patient,simultaneously with ensuring that the laser light beam is all the timeseen as a red spot or a red cross on the rear end face of theneedle-type instrument. The needle is thereby introduced at the correctinsertion angle. In the usual way, the insertion distance or depth hasbeen marked on the needle by means of steristrip (sterile, narrowadhesive tape) if there is no centimetre or millimetre scale on theneedle.

Any further features of the present invention will appear from theattached claims, as well as from the following description of theinvention with reference to the attached drawings describingnon-limitative examples of embodiments according to the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of the present device with a computedtomography apparatus.

FIG. 2 is a simplified version of the apparatus according to theinvention in a prototype embodiment.

FIGS. 3 and 4 are perspective views from opposite sides of the apparatusaccording to the invention.

FIG. 5 is a detail of the apparatus at an enlarged scale.

FIGS. 6, 7 and 8 are further detailed views of the apparatus, accordingto the invention.

FIG. 9 is a detailed, partly cut-away view of a part of the apparatus,according to the invention.

FIG. 10 is a partial schematic view of the detailed partial embodimentshown in FIG. 9.

FIG. 11 is a schematic view from above of the embodiment of FIG. 10.

FIG. 12 is a x, y, z diagram to illustrate insertion entry point andtarget in a single plane.

FIG. 13 is an x, y, z diagram illustrating insertion entry point in oneplane and a target inside the body in another, parallel plane.

FIG. 14 is a display image of an insertion entry point and target in asingle plane.

FIGS. 15a, 15 b, and 15 c illustrate insertion entry point and target indifferent planes, as indicated in FIG. 13.

FIG. 16 is a simplified block diagram of a device for calculatingtransversal insertion angle, craniocaudal insertion angle and insertiondepth.

FIG. 17 is an enlarged diagram for understanding the mathematics of acalculating transversal insertion angle, craniocaudal angle andinsertion depth.

FIGS. 18-20 illustrate alternative ways of mechanically supporting thedevice, according to the invention.

FIGS. 21a and b and FIG. 22 are CT-slices of a first medical case withtraditional biopsy technique.

FIGS. 23a, 23 b, 23 c, 23 d and 23 e are CT-slices of a third medicalcase using the method and apparatus of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A computed tomography apparatus, in the remaining description defined asCT apparatus (FIG. 1). The CT apparatus 1 has a patient supporting table2 which is slidable along a support 3 having means therein for movingsaid table 2 at least partly through a scanner opening 4 in theapparatus 1 by means of motors inside the support 3 providingincremental movement modes of said table 2 on which a patient 5 to beexamined is placed. The CT apparatus has inside in a manner known per seand not to be described further a rotary scanner moving along a circularformed slit 6 as indicated on FIG. 1.

The apparatus for assisting percutaneous computed tomography-guidedsurgical activity inside the body of a human, such as the patient 5, isgenerally indicated by reference numeral 7. In a non-limited embodimentof the invention the apparatus 7 consists of a base member 8, uprightmembers 9 and 9′, which are preferably telescopically mounted andmutually lockable by means of a locking handle 10. Further, theapparatus 7 has a transverse member 11 extending from a top region ofthe upright member 9′. The apparatus 7 has a unit 12 moveable along thetransverse member 11 and lockable in position there along. The unit 12has laser beam generator device 13 including a power supply means 14(FIG. 11) for the device 13. Said power supply means 14 has suitably anon/off switch 15. The laser beam generator device 13 has suitably apower inlet terminal 16 show in FIGS. 10-11. Based on calculations to beexplained further, transverse insertion angle and craniocaudal insertionangle can be calculated. Using, e.g., turning knob 17, the transversalinsertion angle to be described by a laser beam 13′ can be set.Similarly, the craniocaudal insertion angle can be set for the beam 13′by means of an adjustment knob 18 (FIG. 9). The turning of the knob 17is a movement which is transferred through a gear box 17′ to atwo-dimensional turning device 19 having an outer ring and inner ringwhich are moveable relative to each other. Thus, viewing FIG. 11 turningof knob 17 means that the laser device 13 will be moveable in thedirection of the long side of the drawing sheet. Movement of theadjustment knob 18 via a first gear box 18′ and a second gear box 18″will yield that the ring 21 will move relative to ring 20 in order to beable to move the laser device 13 parallel to the short side of thedrawing sheet. The gear box 17′ and suitably also the gear box 18″ mayhave angle indicators in order that an operator of the inventiveapparatus may know when the set angles have been reached.

The laser beam generating device 13 receives power from the power supply14 via connecting wires 22. A display for indication of e.g. thecraniocaudal insertion angle has been schematically indicated on FIG. 10by reference numeral 23. The angle indicator has also been shown as anexample on FIG. 6. Similarly, as shown on FIG. 6, an angle indicator forthe transversal insertion angle has been indicated by reference numeral24. As indicated on FIG. 8, a calculator device 25 could form anintegral part of the apparatus and e.g. be locatable on an end part ofthe transverse member 11, as indicated on FIG. 6 by reference numeral11′. Based on x and y values obtained from tomography image co-ordinatevalues, it will be possible to calculate the transversal insertion angleand craniocaudal insertion angle and have those angle values shown ondisplays 25′ and 25″.

As shown on FIGS. 6 and 7, the unit 12 is moveable along the transversemember 11 and can be locked in any position therealong by means oflocking members 26 releasable by pushing knobs 27. In a particularembodiment, it is considered possible to move the unit 12 over atransition region 28 between the transverse member 11 and the uprightmember 9′.

Suitably, a radome 29 is located below the exit of laser beam generatordevice 13, said radome 29 (FIG. 5) being of a material and thicknesscausing little or negligible refraction of the laser beam 13 when itpasses through the radome material. Suitably, the exit of the laser beamgenerator device 13 is close to the inner surface of the radome. Theradome is primarily for protecting the laser beam generator device 13against damage caused by accidental impacts.

A more simplified version of the apparatus, according to the invention,forming a prototype of the apparatus is shown in more detail on FIG. 2.The apparatus has a transverse top beam 11 which is connectable to anupright member 9, 9′. The transverse member 11 has suitably a pair ofslide rails 30, 31 with slide shoes 32, 33, 34, 35 attached to a commonplate member 36. The plate 36 is attached to a unit 37 via a hingeconnection 38 and a craniocaudal angle adjustment of connection 39. Theunit 38 consists of a laser beam generator device 40, suitably of thesame type as denoted by reference numeral 13 in connection with thedisclosure of the embodiment shown on FIGS. 1, 3-11. Further, said unit37 has suitably a level 41 for indicating a craniocaudal insertion angleequal to 0 degrees as also indicated by an angle indicator 42. Atransversal insertion angle indicator 43 is also located on unit 37 andis provided with a fixation knob 44. When the proper transversalinsertion angle and craniocaudal insertion angle have been calculated,the laser beam 40′ will point at the correct insertion point 5′ on thebody of the patient 5. The needle-type surgical instrument to beinserted into the body of the patient 5 is denoted by reference numeral45 on FIG. 2. The instrument 45 is to be hand-held by a surgeon. At adistal end 46 of the instrument, there is located an aiming point orface 46′, suitably, but not necessarily, made of a light reflectivematerial. Thus, keeping in mind that the laser beam 40′ is directed topoint with correct transversal insertion angle and craniocaudal angle atthe insertion point 5′, inserting the instrument at the insertion point5′ and ensuring that the aiming point or face 46′ is always hit by thelaser beam 40′, will ensure that the instrument is moved correctly intothe body of the patient 5. Although the laser beam 40′ may create only alight spot on the distal end 46 of the instrument, the laser beam couldbe of a cross-hair type, thus more readily defining a centre point onsaid distal end 46.

In a manner known per se the needle portion 47 of the instrument 5 has alength scale, e.g. in metric units such as centimetres, to be able toobserve the correct insertion depth of needle portion 47.

Thus, by knowing the correct transversal insertion angle and thecraniocaudal insertion angle, as well as the insertion depth, a safeinsertion of the needle portion 47 of the instrument 45 into the body ofthe patient 5 can be made.

The instrument is suitable for withdrawal of body tissue or body liquidsample, withdrawal of excess body fluid, insertion or injection. In apreferred application of the present invention, the instrument issuitable for taking a body tissue or body liquid sample, e.g. known asaspiration cytology, percutaneous fine needle biopsy or surgical microbiopsy.

A most important advantage of the present invention over the prior artis the feature of the apparatus being in physical non-contact with theinstrument to be inserted into the patient's body. This is clearly seenfrom FIG. 1. In turn, this means that the apparatus, according to theinvention does not require any disinfection cleaning operation after abiopsy has been performed, contrary to the prior art apparatus forassisting percutaneous computed tomography-guided surgical activityrelated to insertion of a needle-type surgical instrument into a humanor animal body. A further advantage over the prior art is that theoperator may use both hands while introducing the needle, i.e. theoperator does not have to support the instrument with one hand.

Calculation of transversal insertion angle and craniocaudal insertionangle and the combination thereof to obtain the correct direction ofinsertion is now to be further described with reference to FIGS. 12-17.

The insertion point is generally denoted by I, and the target, e.g. amalignant tumour is denoted by T. In the simple example as illustratedby FIGS. 12 and 14, the insertion of the instrument 45 and its needleportion 47 is determined to be made in a single tomography image planewith co-ordinates for the target and the insertion point denoted byco-ordinates x1, y1 and x2, y2, respectively. The angle can becalculated on a separate calculating device based on the co-ordinatevalues or simply be read off from the tomography image viewing screenwhich suitably has cursor means to connect said co-ordinates on thescreen and thereby determine the angle of the cursor relative to thevertical.

In the particular case where it is difficult to let the needle portion47 of the instrument 45 move in a single tomography image slice plane,simply due to internal organs having risk of being punctured by theneedle or be damaged or cause internal bleeding or other damages, it ismore than often required to have the target in a first tomography imageslice plane TP (xT, yT, zT) and the insertion point in a paralleltomography image slice plane IP, such as schematically shown on FIG. 13as well as on FIGS. 15a, 15 b and 15 c. Again, the target is given theco-ordinates x1, y1, z1, z being the direction of the movement of thetable 2. The insertion point is denoted by the co-ordinates x3, y3, z3.Thus, the purpose of understanding the calculation below and withreference to FIG. 17, A=y3−y1, B=z3−z1, and C=x3−x1. Thus, withreference to FIG. 7, the following calculations can be made.

D={square root over (A²+L +B²+L )}

D²=A²+B²

${\tan \quad \angle \quad {tv}} = \frac{C}{D}$${\angle \quad {tv}} = {\tan^{- 1}\frac{C}{D}}$

${{\angle \quad \underset{\_}{C\quad C}}:{\tan \quad \angle \quad C\quad C}} = \frac{A}{B}$${\angle \quad C\quad C} = {\tan^{- 1}\frac{A}{B}}$

 Insertion DepthS={square root over (C²+L +D²+L )}

Thus, by turning the proper adjustment means for transversal insertionangle and craniocaudal angle to obtain the composite direction ofinsertion, as well as the insertion depth, a safe insertion procedure isobtained. Naturally, it will be important to carefully check in astep-by-step fashion, how the insertion proceeds by taking repeated setsof tomography image slices.

On FIG. 16 there is shown in a simplified block diagram form a microprocessor 48 and at the outputs therefrom displays 49 and 50 for showingthe computed craniocaudal insertion angle and the transversal insertionangle, respectively, as well as a display 51 for showing the insertiondepth. The microprocessor 48 calculates the appropriate insertion anglevalues and insertion depth value based on the co-ordinates of theproposed insertion point 5′, denoted by co-ordinates Ix, Iy, Iz, and theco-ordinates of the target T, denoted by co-ordinates Tx, Ty, Tz.

In order to make sure that the transverse member or arm 11; 57; 60 islocated exactly at right angle to the craniocaudal direction, theapparatus is provided with an auxiliary laser beam generator device 63providing a light plane 64 parallel to said craniocaudal direction. Asshown on FIG. 2, the plane 64 will hit and lie along the bed 2, thusindicating that the arm 11 is transversely of the craniocaudaldirection.

The microprocessor 48, its displays 49, 50, 51 and the laser generatordevices 13 and 63 are powered from a power supply 52. As an alternativeto battery operation 52, the apparatus may be powered from the mains 61via an AC to DC converter 62, said DC convertor e.g. delivering 12V DCor 24V DC.

Although, the supporting device may be of a type located on a floor,with reference to FIG. 18, an alternative is to slidably attach theapparatus supporting device to a bed or table base member 53 whichsupports the computed tomography (CT) machine patient supporting movabletable or bed 2. Said supporting device may have a telescopic verticaladjustment means 10. The laser beam generator device 13 is movable alongsaid transverse member or arm 11 as described before.

In the further alternative, with reference to FIG. 19, an apparatussupporting device 54 is suspended from a ceiling 55 above said patientsupporting movable table or bed 2. The supporting device 54 may havemeans, e.g. telescopic vertical adjustment means 56 for adjusting thelevel of a transverse member or arm 57 above the human or animal body 5.The laser beam generator device is movable along said transverse memberor arm 57.

In a still further alternative and with reference to FIG. 19, anapparatus supporting device 58 is suspended from a top region on the CTapparatus 1. The supporting device 58 may have means, e.g. telescopicvertical adjustment means 59 for adjusting the level of a transversemember or arm 60, above the human or animal body 5. The laser beamgenerator device 13 is movable along said transverse member or arm 60.

In order to more fully appreciate the importance of the presentinvention, reference is now directed to attached FIGS. 21a, 21 b, FIG.22 and FIGS. 23a, 23 b, 23 c, 23 d and 23 e.

In FIGS. 21a and 21 b are shown a first medical case showing a tumourhaving a liquid part 70 and a solid tissue part 71. As seen, the tumouris associated with the right lung 72 of the patient. For reference thespine is denoted by reference numeral 73 and the aorta by referencenumeral 74. Further, the heart is denoted by reference numeral 75.

In order to perform a biopsy, the needle part of the biopsy instrument,as denoted by reference numeral 76 is to be inserted into the solidtissue of the tumour. As noted from FIG. 21b the distance required forinsertion and the angle of insertion is denoted by the cursor 77. The CTslice image and evaluation thereof indicates that the insertion angle isto be 90 degrees and the insertion depth to be 3.90 cm.

With such short insertion depth and a well defined insertion angle, thebiopsy is fairly straight forward to perform, even with prior art biopsytechniques.

However, a more complicated and true case, medical case number two, isshown on FIG. 22. This particular case, using the prior art free-handtechnique and aiming the biopsy instrument using eye measures, clearlyindicates the severe risks which are imposed on patient during biopsysample taking. In this particular case an attempt has been made to hitwith the biopsy instrument needle 80 a tumour 81 located in the leftlung 82. As a complication in the biopsy operation, the operator hasmanaged to puncture the lung which has therefore partly collapsed. Theimage shown on FIG. 22 does not represent the first insertion of thebiopsy needle 80. A repeated insertion is represented by FIG. 22 and, asshown, the needle has unintentionally passed very close to the aorta 83,with a very narrow margin. If the aorta had been punctured, a seriousbleeding could have occurred. For reference, the spine has beenindicated by reference numeral 84 and the heart by reference numeral 85.

The medical case of FIG. 22 clearly indicates that insertion angle ofthe biopsy instrument as well as insertion depth in many cases is highlycritical.

It will be appreciated that using the method and apparatus of thepresent invention could all together have avoided the dangeroussituation shown with reference to FIG. 22.

A third medical case, represented by FIGS. 23a-23 e is now to bedescribed very briefly, the biopsy using the technique according to thepresent invention.

In order to more fully understand the CT slice images, reference 90denotes a rib. The left kidney is denoted by reference 91. Aorta isdenoted by reference 92. Interior vena cava is denoted by reference 93.The liver is denoted by reference 94. The medical situation is that thepatient has a collection of liquid in the pancreas, as denoted byreference numeral 95. Situation of post-pancreatitis is denoted byreference numeral 96. Further, pseudo-cysts are denoted by referencenumeral 97. As shown on the images of FIG. 23 it was a prime object toremove the large collection of liquid within the pancreas and inparticular in the pseudo-cysts, as shown on FIG. 23d. It will beappreciated that not only is the insertion depth calculation critical,but the insertion angles are highly critical, in particular with such along biopsy needle or cannula to be used. Notably and as clearly shownon FIG. 23d and 23 e, the needle or cannula, as indicated by referencenumeral 98 is extremely long, almost the cross sectional width of thehuman body at the location of the CT slice image. Without the aid of thepresent method and apparatus, a puncture procedure as shown would takevery long time and involve high risks of not hitting the targetproperly. Thus, with further reference to FIG. 23 the CT slice imagesclearly indicate a very complicated puncture of a series of liquidcollections in the pancreas where a very long needle 98 has beeninserted from the left side of the abdomen transversally towards theright. In the particular case shown, the patient was lying on the rightside. On FIG. 23b the needle has been inserted at a correct angle and acontrol CT slice has been made to check that the needle is on a rightpath. The fact that the complete needle is shown indicates that theinsertion has been made exactly in the transversal plane being the sameas the CT slice image plane.

FIG. 23d indicates the needle 98 being moved further in, and the path ofthe needle is still a correct one. A further advancement of the needleto the liquid collection to the far right of the patient, (next to theliver 94) is shown on FIG. 23e.

After the needle 98 hit the target shown on FIG. 23e, a thin wire wasinserted through the needle to be a pilot wire for a thin tube to beinserted into the human body over the steel wire. The tube (not shown)was for draining the liquid in the pancreas.

Having described my invention, I claim:
 1. A method for assisting percutaneous computed tomography-guided surgical activity inside a human or animal body, said method for determining insertion depth, transverse insertion angle and craniocaudal insertion angle for a needle-type surgical instrument to be inserted into the human or animal body from an insertion entry point on a skin surface of said body to a target inside said body, comprising: determining from a first tomography image first coordinate values for said entry point related to a first tomography slice position along craniocaudal direction, and horizontal and vertical directions transversely of said craniocaudal direction at said first position, determining from a second tomography image second coordinate values for said target point related to a second tomography slice position along craniocaudal direction, and horizontal and vertical directions transversely of said craniocaudal direction at said second position, calculating from said first and second coordinate values through principle of trigonometry values of said insertion depth, transverse insertion angle and craniocaudal insertion angle, and said transverse insertion angle value, said craniocaudal insertion angle value, said first coordinate values, and said second coordinate values defining a direction of insertion and insertion depth from said entry point.
 2. The method according to claim 1, further comprising applying said values of said transverse insertion angle and craniocaudal insertion angle to an instrument insertion guiding apparatus positioned adjacent to said body in no physical contact therewith, said apparatus having a laser which provides a laser beam, manipulating adjustment means on said apparatus to let said laser beam assume said values of transversal insertion angle and craniocaudal insertion angle and to let said laser beam point at said entry point in said defined insertion direction.
 3. The method according to claim 2, further comprising locating said instrument with a needle pointed end thereof at said entry point and aligning a longitudinal axis of said instrument coaxially with said laser beam, said instrument being in no physical contact with said apparatus.
 4. The method according to claim 3, wherein said step of aligning includes letting a distal end face of said instrument be pointed at by said laser beam.
 5. The method according to claim 4, wherein said laser beam provides a light spot on said distal end face.
 6. The method according to claim 4, wherein said laser beam provides a cross-hair like light image on said distal end face.
 7. The method according to claim 3, further comprising positioning a laser carrying arm of said apparatus to lie horizontally above the body at right angles to said craniocaudal direction.
 8. The method according to claim 7, wherein the positioning step includes using a line laser located on said laser carrying arm, said line laser providing a laser line, and aligning said laser line parallel to said craniocaudal direction.
 9. The method according to claim 2, further comprising positioning a laser carrying arm of said apparatus to lie horizontally above the body at right angles to said craniocaudal direction.
 10. The method according to claim 9, wherein the positioning step includes using a line laser located on said laser carrying arm, said line laser providing a laser line, and aligning said laser line parallel to said craniocaudal direction.
 11. A method for assisting percutaneous computed tomography-guided surgical activity inside a human or animal body, said method for determining insertion depth, transverse insertion angle and craniocaudal insertion angle for a needle-type surgical instrument to be inserted into the human or animal body from an insertion entry point on a skin surface of said body to a target inside said body, comprising: determining from a first tomography image first coordinate values for said entry point related to a first tomography slice position along craniocaudal direction, and horizontal and vertical directions transversely of said craniocaudal direction at said first position, determining from said first or a second tomography image second coordinate values for said target point related to said first or a second tomography slice position along craniocaudal direction, and horizontal and vertical directions transversely of said craniocaudal direction at said first or second position, calculating from said first and second coordinate values through principle of trigonometry values of said insertion depth, transverse insertion angle and craniocaudal insertion angle, applying said values of said transverse insertion angle and craniocaudal insertion angle to an instrument insertion guiding apparatus positioned adjacent to said body in no physical contact therewith, said apparatus having a laser which provides a laser beam, manipulating adjustment means on said apparatus to let said laser beam assume said values of transversal insertion angle and craniocaudal insertion angle and to let said laser beam point at said entry point, and locating said instrument with a needle pointed end thereof at said entry point and aligning a longitudinal axis of said instrument coaxially with said laser beam, said instrument being in no physical contact with said apparatus, wherein: said step of aligning includes letting a distal end face of said instrument be pointed at by said laser beam, and said laser beam provides a cross hair-like light image on said distal end face.
 12. The method according to claim 11, further comprising positioning a laser carrying arm of said apparatus to lie horizontally above the body at right angles to said craniocaudal direction.
 13. The method according to claim 12, wherein the positioning step includes using a line laser located on said laser carrying arm, said line laser providing a laser line, and aligning said laser line parallel to said craniocaudal direction.
 14. A method for assisting percutaneous computed tomography-guided surgical activity inside a human or animal body, said method for determining insertion depth, transverse insertion angle and craniocaudal insertion angle for a needle-type surgical instrument to be inserted into the human or animal body from an insertion entry point on a skin surface of said body to a target inside said body, comprising: determining from a first tomography image first coordinate values for said entry point related to a first tomography slice position along craniocaudal direction, and horizontal and vertical directions transversely of said craniocaudal direction at said first position, determining from a second tomography image second coordinate values for said target point related to a second tomography slice position along craniocaudal direction, and horizontal and vertical directions transversely of said craniocaudal direction at said second position, calculating from said first and second coordinate values through principle of trigonometry values of said insertion depth, transverse insertion angle and craniocaudal insertion angle, said transverse insertion angle value, said craniocaudal insertion angle value, said first coordinate values, and said second coordinate values defining a direction of insertion and insertion depth from said entry point, applying said values of said transverse insertion angle and craniocaudal insertion angle to an instrument insertion guiding apparatus positioned adjacent to said body in no physical contact therewith, said apparatus having a laser which provides a laser beam, manipulating adjustment means on said apparatus to let said laser beam assume said values of transversal insertion angle and craniocaudal insertion angle and to let said laser beam point at said entry point, and locating said instrument with a needle pointed end thereof at said entry point and aligning a longitudinal axis of said instrument coaxially with said laser beam, said instrument being in no physical contact with said apparatus, wherein: said step of aligning includes letting a distal end face of said instrument be pointed at by said laser beam, and said laser beam provides a light spot on said distal end face.
 15. The method according to claim 14, further comprising positioning a laser carrying arm of said apparatus to lie horizontally above the body at right angles to said craniocaudal direction.
 16. The method according to claim 15, wherein the positioning step includes using a line laser located on said laser carrying arm, said line laser providing a laser line, and aligning said laser line parallel to said craniocaudal direction.
 17. A method for assisting percutaneous computed tomography-guided surgical activity inside a human or animal body, said method for determining insertion depth, transverse insertion angle and craniocaudal insertion angle for a needle-type surgical instrument to be inserted into the human or animal body from an insertion entry point on a skin surface of said body to a target inside said body, comprising: determining from a first tomography image first coordinate values for said entry point related to a first tomography slice position along craniocaudal direction, and horizontal and vertical directions transversely of said craniocaudal direction at said first position, determining from a second tomography image second coordinate values for said target point related to a second tomography slice position along craniocaudal direction, and horizontal and vertical directions transversely of said craniocaudal direction at said second position, calculating from said first and second coordinate values through principle of trigonometry values of said insertion depth, transverse insertion angle and craniocaudal insertion angle, said transverse insertion angle value, said craniocaudal insertion angle value, said first coordinate values, and said second coordinate values defining a direction of insertion and insertion depth from said entry point, applying said values of said transverse insertion angle and craniocaudal insertion angle to an instrument insertion guiding apparatus positioned adjacent to said body in no physical contact therewith, said apparatus having a laser which provides a laser beam, manipulating adjustment means on said apparatus to let said laser beam assume said values of transversal insertion angle and craniocaudal insertion angle and to let said laser beam point at said entry point, locating said instrument with a needle pointed end thereof at said entry point and aligning a longitudinal axis of said instrument coaxially with said laser beam, said instrument being in no physical contact with said apparatus, wherein: said step of aligning includes letting a distal end face of said instrument be pointed at by said laser beam, and said laser beam provides a cross hair-like light image on said distal end face.
 18. The method according to claim 17, further comprising positioning a laser carrying arm of said apparatus to lie horizontally above the body at right angles to said craniocaudal direction.
 19. The method according to claim 18, wherein the positioning step includes using a line laser located on said laser carrying arm, said line laser providing a laser line, and aligning said laser line parallel to said craniocaudal direction.
 20. A method for assisting percutaneous computed tomography-guided surgical activity inside a human or animal body, said method for determining insertion depth, transverse insertion angle and craniocaudal insertion angle for a needle-type surgical instrument to be inserted into the human or animal body from an insertion entry point on a skin surface of said body to a target inside said body, comprising: determining from a first tomography image first coordinate values for said entry point related to a first tomography slice position along craniocaudal direction, and horizontal and vertical directions transversely of said craniocaudal direction at said first position, determining from said first or a second tomography image second coordinate values for said target point related to said first or a second tomography slice position along craniocaudal direction, and horizontal and vertical directions transversely of said craniocaudal direction at said first or second position, calculating from said first and second coordinate values through principle of trigonometry values of said insertion depth, transverse insertion angle and craniocaudal insertion angle, applying said values of said transverse insertion angle and craniocaudal insertion angle to an instrument insertion guiding apparatus positioned adjacent to said body in no physical contact therewith, said apparatus having a laser which provides a laser beam, manipulating adjustment means on said apparatus to let said laser beam assume said values of transversal insertion angle and craniocaudal insertion angle and to let said laser beam point at said entry point, locating said instrument with a needle pointed end thereof at said entry point and aligning a longitudinal axis of said instrument coaxially with said laser beam, said instrument being in no physical contact with said apparatus, and positioning a laser carrying arm of said apparatus to lie horizontally above the body at right angles to said craniocaudal direction, wherein the positioning step includes using a line laser located on said laser carrying arm, said line laser providing a laser line, and aligning said laser line parallel to said craniocaudal direction.
 21. A method for assisting percutaneous computed tomography-guided surgical activity inside a human or animal body, said method for determining insertion depth, transverse insertion angle and craniocaudal insertion angle for a needle-type surgical instrument to be inserted into the human or animal body from an insertion entry point on a skin surface of said body to a target inside said body, comprising: determining from a first tomography image first coordinate values for said entry point related to a first tomography slice position along craniocaudal direction, and horizontal and vertical directions transversely of said craniocaudal direction at said first position, determining from a second tomography image second coordinate values for said target point related to a second tomography slice position along craniocaudal direction, and horizontal and vertical directions transversely of said craniocaudal direction at said second position, calculating from said first and second coordinate values through principle of trigonometry values of said insertion depth, transverse insertion angle and craniocaudal insertion angle, said transverse insertion angle value, said craniocaudal insertion angle value, said first coordinate values, and said second coordinate values defining a direction of insertion and insertion depth from said entry point, applying said values of said transverse insertion angle and craniocaudal insertion angle to an instrument insertion guiding apparatus positioned adjacent to said body in no physical contact therewith, said apparatus having a laser which provides a laser beam, manipulating adjustment means on said apparatus to let said laser beam assume said values of transversal insertion angle and craniocaudal insertion angle and to let said laser beam point at said entry point in said defined insertion direction, locating said instrument with a needle pointed end thereof at said entry point and aligning a longitudinal axis of said instrument coaxially with said laser beam, said instrument being in no physical contact with said apparatus, and positioning a laser carrying arm of said apparatus to lie horizontally above the body at right angles to said craniocaudal direction, wherein the positioning step includes using a line laser located on said laser carrying arm, said line laser providing a laser line, and aligning said laser line parallel to said craniocaudal direction. 